Construction element made of adobe

ABSTRACT

The present invention relates to a construction element ( 1 ) made of compressed clay adobe, capable of being joined, on at least one of the surfaces ( 4 ) thereof, with an adjacent element via a layer including an activatable gellable mixture ( 5 ) extending over the at least one surface ( 4 ) of the element. The invention also relates to a method for assembling a portion of a building using such elements ( 1 ).

FIELD OF THE INVENTION

The invention relates to construction elements made of compressed adobe.

The invention also relates to a method for assembling a portion of a building using such elements.

INTRODUCTION

Adobe has been used as a construction material for thousands of years. It continues to be the most widely used construction material worldwide. One third of the human race lives in a home made of adobe, i.e. over two billion people in 150 countries, most often in the Third World.

Stabilised adobe has also been the subject of interest in Western countries particularly due to the properties thereof which are in line with a sustainable development approach: excellent durability, reduction of transport and processing costs (particularly without any energy expenditure), high thermal inertia, easy recycling of debris, etc. The stabilisation of clay adobe, which is intended to reduce the water sensitivity thereof and increase the strength thereof, may be performed by compression/compaction and/or by means of a chemical process, for example by adding lime. There are various techniques for using stabilised adobe, including rammed clay and compressed clay blocks. However, these techniques require a large amount of time and labour.

Further advantages of adobe lie in the fireproof and healthy, particularly hypoallergenic, nature thereof.

Moreover, the use of adobe is also of aesthetic interest, since it enables great architectural variety along with shapes of complex appearances: walls, partitions, arches, domes, cornices, decorative facade elements, etc.

Architects and contractors working with adobe are striving to spread this construction method of the future, which is economical, healthy and flexible in respect of the applications thereof and has a small environmental footprint. For this purpose, these contractors aim to increase the quality of their buildings and their productivity while reducing labour costs as much as possible.

STATE OF THE RELATED ART

Such construction elements made of compressed clay adobe are known, for example, in the document FR 2 861 010 disclosing a method for prefabricating stabilised architectonic elements made of rammed earth. However, the assembly of these elements is not described therein.

This observation also applies for the application FR 2 527 136 relating to a method for stabilising construction elements made of compressed clay by means of dynamic compaction of a clay-water-binder mixture with a free falling mass.

The documents FR 2 936 534 and FR 2 509 344 relate to stabilised compressed clay blocks having profiles enabling the interlocking and self-alignment thereof for assembling walls. The blocks are rigidly connected together with adhesive or mortar.

The international application WO 1986/06 126 relates to self-interlocking blocks made of cold-stabilised hypercompressed blocks for joint-free wall building. The stability of these blocks is provided by liquid mortar injections.

The document FR 2 638 187 relates to a construction block made of compressed clay wherein the exposed surfaces each consist of an erosion protection plate. The connection between the blocks is provided using mortar as a binder.

The international application WO 2008/062 299 relates to stabilised clay blocks comprising an inner portion made of non-stabilised clay and a thin layer of stabilised clay on one or two surfaces, wherein said surfaces serve to protect the wall constructed with such blocks against moisture, weathering and abrasion. The clay blocks are connected with mortar.

In these five documents mentioned above, the compressed clay blocks described are assembled traditionally using means such as adhesive or mortar.

These traditional means involve a number of drawbacks. Firstly, they only enable superficial adherence between the construction elements. Moreover, the manufacture thereof generally requires a non-negligible amount of energy and the recycling thereof after the demolition of buildings assembled in this way is difficult, which is unfavourable for the environmental footprint thereof. Moreover, the impregnation of the surfaces of the construction elements during assembly is time-consuming, which impedes productivity.

SUMMARY OF THE INVENTION

One aim of the invention is that of providing a construction element made of compressed clay adobe having properties which are in line with sustainable development while enabling the production of portions of buildings under optimal conditions in respect of mechanical strength (stability) and productivity.

The term construction element denotes in the present application any element, whether supporting or not, suitable for being used in the field of construction, such as a masonry element, a partition element, a floor element, an exterior or interior cladding element, an exterior or interior decorative element, etc.

For this purposes, the construction element made of compressed adobe according to the invention is suitable for being joined on at least one of the surfaces thereof with an adjacent element via a layer including an activatable gellable mixture extending over the at least one surface of the element. This layer may be obtained in various ways, for example by applying a coating or by filling in a mould.

Once activated, this gellable mixture is liable to cause the surfaces of the adjacent elements in contact to react with each other over a specific depth. As a result, in the contact area, the materials interact and are joined under the effect of physicochemical phenomena, interconnecting the elements in-depth without forming a joint and thus promoting the stability of the portions of buildings assembled in this way.

The advantage of this method is that of being able to use natural elements which are plentiful and non-toxic for this gellable mixture, which does away with any problems in respect of transporting and/or recycling construction waste.

A further aim of the invention is that of achieving a particular aesthetic effect using a type of adobe which is generally neglected due to the mechanical properties thereof.

For this purpose, the clay adobe used in the construction elements according to the invention is characterised by a plasticity index preferably between 10 and 35 (indicative values for “plastic” clays), and more preferably greater than 35 (indicative values for “highly plastic” clays such those comprising smectite including bentonite). These clays, routinely used in the field of pottery and the earthenware industry, give the construction element a very low surface porosity and thus a higher quality finish.

Advantageously, the clay adobe is supplemented with 3 to 10% lime by weight before compression. On stabilising, these contents enable, surprisingly, short, medium and long-term pozzolanic reactions to have a very beneficial extent, particularly when using plastic to highly plastic clays, for durability and for the erosion and compression resistance of the construction element according to the invention.

The clay adobe advantageously comprises insofar as possible a smectite to be chosen from montmorillonite and any type of bentonite, preferably containing calcium. These smectite contents promote the waterproofing and thus the frost resistance of the construction elements.

Advantageously, the activatable gellable mixture incorporated in the construction element comprises smectite having a moderate swelling potential, to be chosen from montmorillonite and any type of bentonite, preferably containing calcium. These clays, which may swell during activation, amplify the aggregation phenomenon at the interface between adjacent elements. Moreover, they are, when the elements are stabilised with lime, the most reactive in respect of same and stimulate pozzolanic reactions of lime, maximising the stabilisation of the construction.

The activatable gellable mixture preferably comprises siliceous sand or any other permeable inert material, having a grain size between 0.02 and 5 mm. This ensures in-depth activation of the layer of activatable gellable mixture, which may further comprise fine clay particles having a plasticity index greater than 35.

Advantageously, the construction element according to the invention comprises, on at least one of the aggregation surfaces thereof, grooves suitable for engaging, following activation, with the grooves of the adjacent element which are arranged perpendicularly to the grooves of the first element, so as to accentuate the aggregation of the elements together. These features provide benefits particularly in terms of quality (stability) of the construction and productivity.

A further aim of the invention is that of providing a method for assembling a portion of a building using clay adobe elements having properties in line with sustainable development requirements, enabling the production thereof under optimal conditions in respect of mechanical strength (stability) and productivity.

For this purpose, the method for assembling a portion of a building according to the invention comprises the provision of a mould and the filling thereof with a clay adobe which is subsequently compressed. A construction element is thus formed and then removed from the mould. A layer comprising an activatable gellable mixture is then present on at least one of the surfaces of the construction element which is then dried. During implementation, the surfaces to be assembled of first and second construction elements are washed or sprayed so as to activate the gellable mixture. These surfaces are placed in contact and pressed against each other. Under the effect of the activated gelled mixture, the contact zone softens and may swell slightly. The two adjacent elements are joined. The portion of the building is then left to dry.

The portions of buildings produced according to the method according to the invention have, due to the mutual aggregation of the constituent construction elements, an increased mechanical strength, which is advantageous, particularly in areas with seismic activity.

This method also has the advantage that the operations for applying the layer of gellable mixture and washing for the reactivation thereof are both extremely simple and quick. This technique thus promotes productivity and accessibility to low-skilled labour encountered in large numbers in low-income countries.

Besides the socio-economic advantages thereof, the method according to the invention also has a favourable impact on the environment and sustainable development. It particularly enables the reuse of local non-agricultural clays which, in many cases, are an almost inexhaustible source of material. The method requires practically no energy and does not use chemicals. Moreover, the constructions are, after demolition, readily recyclable.

As a general rule, the assembly method according to the invention fits in perfectly with the development of an economy focussing on profitability, durability and improving human living conditions. Furthermore, it is applicable practically everywhere, regardless of the level of local development in question.

Advantageously, the operation for filling the mould with clay adobe is simultaneous with the operation for producing the layer comprising the activatable gellable mixture. According to one preferred embodiment, a layer of the activatable gellable mixture is placed on at least one of the surfaces of the mould, the remainder of the volume consisting of clay adobe. These alternative embodiments make it possible to envisage more automated manufacture of the construction elements.

Moreover, the method according to the invention also has an aesthetic impact, since, due to the aggregation of the construction elements forming the portion of the building, there are no joints, except in the case of moulded joints on manufacturing the element. The portion of the building may thus have the external appearance of a covering, making it possible to save on the application of a levelling coat.

In the method according to the invention, the operation for drying the construction element is advantageously oven-drying, which is preferably performed at 100° C. and 100% humidity. The drying may also take place in an autoclave under vapour pressure. These arrangements result, if the construction elements are stabilised with lime, in a very pronounced amplification of the reaction between the clay and the lime and the control thereof, making it possible both to ensure consistency of the physical and above all mechanical characteristics for an entire production run and increase productivity.

Advantageously, the elements are stored in such a way as to preserve the humidity obtained during the oven-drying or autoclave vapour treatment as long as possible. Maintaining this humidity prevents any lime carbonation and thus maximises the lime available for pozzolanic reactions, increasing the extent thereof and thus enhancing the stability of the elements.

According to the invention, the wash is preferably a limewash.

Moreover, the wash may comprise fine clay particles having a plasticity index greater than 35 and/or a small quantity of siliceous sand or any other conductive material of the wash. This conductive material should enable, by enabling easier penetration of the wash in the activatable gellable layer, the in-depth activation thereof.

In the assembly method according to the invention, a clay adobe having a plasticity index preferably between 10 and 35, and more preferably greater than 35 is advantageously used. These clays, routinely used in the field of pottery and the earthenware industry, give the construction element a very low surface porosity and thus a higher quality finish.

According to the assembly method according to the invention, clay adobe comprising 3 to 10% by weight of lime before compression is advantageously used. On stabilising, these contents enable, surprisingly, short, medium and long-term pozzolanic reactions to have a very beneficial extent, particularly when using plastic to highly plastic clays, for durability and for the erosion and compression resistance of the construction element according to the invention.

Advantageously, clay adobe comprising insofar as possible a smectite to be chosen from montmorillonite and any type of bentonite, preferably containing calcium, is used. These smectite contents promote the waterproofing and thus the frost resistance of the construction elements.

A gellable mixture comprising smectite having a moderate swelling potential, to be chosen from montmorillonite and any type of bentonite, preferably containing calcium, is advantageously used in the assembly method according to the invention. These clays, which may swell during activation, amplify the aggregation phenomenon at the interface between adjacent elements.

According to the assembly method according to the invention, a gellable mixture comprising fine clay particles having a plasticity index greater than 35 is preferably used. Advantageously, this mixture also contains siliceous sand or any other permeable inert material, having a grain size between 0.02 and 5 mm so as to ensure in-depth penetration of the wash in the layer of gellable mixture.

BRIEF DESCRIPTION OF THE FIGURES

These aspects along with further aspects of the invention will be clarified in the detailed description of particular embodiments of the invention, with reference to the drawings in the figures, wherein:

FIG. 1 schematically represents a perspective view of a portion of a building (in this case, a construction block) according to the method according to the invention;

FIGS. 2 a to 2 c and FIG. 3 are sectional views along the plane II-II in FIG. 1 of various stages of assembly of two construction elements in FIG. 1.

FIGS. 4 a and 4 b show a construction element according to the invention provided with grooves on the assembly surfaces thereof.

FIG. 5 shows the operation for filling with clay adobe and activatable gellable mixture before compression according to one embodiment of the method according to the invention.

The figures are not drawn to scale. As a general rule, similar elements are denoted by similar references in the figures.

DETAILED DESCRIPTION OF PARTICULAR EMBODIMENTS

FIG. 1 shows a construction element (in this case a building block) 1 cut along a plane II-II.

FIG. 2 a shows the cross-section of this construction element 1 wherein two surfaces 4 are provided with a layer comprising an activatable gellable mixture 5. During the assembly of two elements 1 on the surface 4, an activator, or in this case a limewash 7, is applied on this surface (FIG. 2 b). This results in the mixture 5 changing to the activated state 9. After assembly (FIG. 2 c), physicochemical phenomena disrupt, under the effect of the activation of the gel-type mixture 9, the contact area 11 between the two elements 1. Indeed, pozzolanic reactions, softening and swelling effects and other physical effects (for example: diffusion, electrical phenomena, etc.) move the boundaries of this area 11 towards the interior of each of the elements 1 in the direction of the arrows 13, resulting in the two elements 1 joining together, as represented in FIG. 3. The two elements 1 finally merge into a single element without forming a discernable joint.

The bond between the elements 1 is thus not superficial but extends in-depth. Moreover, the effects of swelling cause, by reaction, further compression along the arrows 15 in each element 1. These aggregation and compression phenomena are beneficial for the stability of a portion of a building consisting of such construction elements 1.

If lime is added to the clay adobe forming the construction elements 1, pozzolanic reactions take place within the clay adobe. The resulting stabilisation of the elements 1 is essentially due to the dissolution of the clay minerals in the alkaline environment created by the lime and the recombination of the silica (SiO₂) and alumina (Al₂O₃) (generally found in highly plastic clay adobes) in clays and feldspars in the presence of calcium to form aluminium and calcium complex silicates cementing inert particles (of quartz, for example) together. The pozzolanic reactions are amplified further in the event of oven-drying or autoclave vapour pressure treatment of the construction elements, which helps smooth the mechanical performances of the construction elements, which thus particularly become suitable as supporting elements. The calcium in question is obtained equally well from the adobe and the limewash when it has diffused into the adobe during assembly.

FIGS. 4 a and 4 b show a construction element 1 provided with longitudinal grooves on the top surface 4 thereof and with transverse grooves on the bottom surface 4 thereof. The grooves of the top surface 4 receive the wash. The surfaces are grooved in order to increase the contact surface area developed with the wash and thus the extent of the activation and the subsequent physicochemical phenomena. The perpendicular arrangement of the grooves of adjacent overlaid elements 1 means that there is no interlocking of the grooves, preventing an overflow of limewash towards the shoulders 17 and thus a loss of product for activating the activatable gellable layer. The distance between the shoulders 17 of two overlaid adjacent elements 1 is used to control the subsidence of the contact area resulting from the activation. Moreover, the mutually perpendicular arrangement of the grooves also aids the subsidence of the contact area, following activation, of two overlaid adjacent elements 1. During this subsidence, the grooves reduce in size as the contact area subsides and force the limewash to diffuse within the elements 1. Consequently, the grooves have a favourable impact on the quality of the construction and the productivity of the method.

FIG. 5 shows, in four phases (5.1 to 5.4), the operation for filling a mould, wherein three layers are successively formed: a first layer of activatable gellable mixture followed by a layer of clay adobe, followed by a second layer of activatable gellable mixture. The whole consisting of these three layers is then compressed (phase 5.5). Unlike coating, a water-free gellable layer is used.

It would be obvious for those skilled in the art that the present invention is not limited to the examples illustrated and described above. The invention includes each of the novel features and the combination thereof. The presence of reference numbers cannot be considered to be limiting. The use of the term “comprises” can in no way exclude the presence of further elements other than those mentioned. The use of the indefinite article “a” to introduce an element does not exclude the presence of a plurality of these elements. The present invention has been described with reference to specific embodiments, which are merely illustrative in nature and should not be considered to be limiting. 

1. A construction element made of compressed adobe, suitable for being joined on at least one of the surfaces thereof with an adjacent element via a layer including an activatable gellable mixture extending over the at least one surface of the element.
 2. The construction element according to claim 1, wherein the clay adobe has a plasticity index between 10 and
 35. 3. The construction element according to claim 1, wherein the clay adobe has a plasticity index greater than
 35. 4. The construction element according to claim 1, wherein the clay adobe comprises 3 to 10% lime by weight.
 5. The construction element according to claim 1, wherein the clay adobe comprises a smectite to be chosen from montmorillonite and any type of bentonite.
 6. The construction element according to claim 1, wherein the activatable gellable mixture comprises smectite having a moderate swelling potential, to be chosen from montmorillonite and any type of bentonite.
 7. The construction element according to claim 6, wherein the bentonite is of the type containing calcium.
 8. The construction element according to claim 1, wherein the activatable gellable mixture comprises fine clay particles having a plasticity index greater than
 35. 9. The construction element according to claim 1, wherein the activatable gellable mixture comprises siliceous sand or any other permeable inert material, having a grain size between 0.02 and 5 mm.
 10. The construction element according to claim 1, comprising, on at least one of the aggregation surfaces thereof, grooves suitable for engaging, following activation, with the grooves of the adjacent element which are arranged perpendicularly to the grooves of the first element, so as to accentuate the aggregation of the elements together.
 11. A method for assembling a portion of a building using compressed clay adobe elements, comprising the following operations: a) providing a mould; b) filling the mould with clay adobe; c) compressing the adobe; d) releasing the construction element formed from the mould; e) producing a layer comprising an activatable gellable mixture on at least one of the surfaces of the construction element; f) drying the element; g) storing the element; h) washing the surfaces to be assembled of first and second construction elements, so as to activate the gellable mixture; i) contacting and pressing the surfaces against each other; j) softening and swelling the contact area under the effect of the activated gel-type mixture; k) joining the two adjacent elements; and l) drying the portion of the building.
 12. The method for assembling a portion of a building according to claim 11, wherein operation e) is performed simultaneously with operation b).
 13. The method for assembling a portion of a building according to claim 12, wherein a layer of the activatable gellable mixture is placed on at least one of the surfaces of the mould, the remainder of the volume consisting of clay adobe.
 14. The method for assembling a portion of a building according to claim 11, wherein operation e) is performed by applying a coating comprising the activatable gellable mixture after operation b).
 15. The method for assembling a portion of a building according to claim 11, wherein the operation for drying the element is selected from oven-drying and an autoclave vapour pressure treatment.
 16. The method for assembling a portion of a building according to claim 11, wherein the wash is a limewash.
 17. The method for assembling a portion of a building according to claim 11, wherein the wash comprises fine clay particles having a plasticity index greater than
 35. 18. The method for assembling a portion of a building according to claim 11, wherein the clay adobe has a plasticity index between 10 and
 35. 19. The method for assembling a portion of a building according to claim 11, wherein the clay adobe has a plasticity index greater than
 35. 20. The method for assembling a portion of a building according to claim 11, wherein the clay adobe comprises 3 to 10% lime by weight.
 21. The method for assembling a portion of a building according to claim 11, wherein clay adobe comprises a smectite to be chosen from montmorillonite and any type of bentonite.
 22. The method for assembling a portion of a building according to claim 11, wherein the gellable mixture comprises smectite having a moderate swelling potential, to be chosen from montmorillonite and any type of bentonite.
 23. The method for assembling a portion of a building according to claim 11, wherein the gellable mixture comprises fine clay particles having a plasticity index greater than
 35. 